My wife,a grade school teacher wanted to do this in the 1990s. We picked the trail up in Omaha and for 3 weeks tried to stay as close as possible to the most traveled routes. We ended up at the site of Fort Clatsop near Astoria OR. In those days it was really pretty hard since there were few markers and many keep out signs. In many places you are miles away from the actual route. Been back over a lot of that route and have found much more tourist friendly in recent years. The Arch in Omaha has good information and the Bridge exhibit over freeway as you enter NE is outstanding. There is or was a web site dedicated to the subject.